My dad had colon cancer (13 feet of his colon removed, thank goodness we caught it in time!) about 10 years ago (I recall it being the winter of 2004 maybe?). Can that be seen by his natal? Just curious!
Jupiter rules his 6th house and is in his 6th house. Virgo rules the digestive track and that is the ruler of his 12th house. His Mercury isn't in poor condition and the only negative aspect it makes is a square to Neptune in the 1st.
In my opinion....
Health is Energy. How we manifest our physical bodies is represented by both the challenges of the secondary progressed chart and the natal tendencies of the birth chart. How we are impacted by circumstances is shown by transits, but now more than ever, you need more than one transit and the transiting planet must have a relationship in the natal chart.
I use the Astrodynes extensively here: the power and friction of the planets, houses, signs, and aspects, are very important in making determinations through all the data in the energy chart.
I look at health first through the planets, then the Uranian Planets and Transpluto, then Dark Moon Lilith, and then the fixed stars. Next I look at the signs, by looking at planets in the signs. This is followed by looking at the Crosses. I look to see which kind of cross exists in the chart: planets in all four of the signs(including the Ascendant or MH as a planet): Cardinal( Aries, Cancer, Libra, Capricorn) Fixed( Taurus, Leo, Scorpio, Aquarius) or mutable( Gemini, Virgo, Sagittarius, Pisces)
Next I look at the power and strength of the houses, with particular attention to the 6th and the 12th houses of illness not life threatening, and illness possibly life threatening.
The sign the planet is in will indicate where the illnesses will occur, the house will show why the illnesses occur, the aspects will show the severity of the illness. Hard aspects create stress that may manifest as physical ailments. There are four important hard aspects: conjunction, square, opposition, and inconjunct. Two other minor aspects, the semi square(45) and the sesiquiquadrant(135) can provide irritation and abrasion that eventually breaks down an organ system.
So then I look at hard aspects between the planets, and including Dark Moon Lilith.
Finally I look at significant midpoint configurations, with planets and with the Uranians. I have to see these as supporting not causing actions. If the planet that is the midpoint planet is very powerful or very high friction, this increases the effect of the mid point. Like wise if the two planets that have a midpoint are high power or high friction, then this increases the impact of the midpoint picture. Finally if the planetary aspect between the two planets if powerful or high friction AND the apex planet is also high friction or high power this is a double whammy. I also use asteroids and the Uranians as the apex planet.